SSC CHSL Model Paper 6

If D is Male, the answer is Nephew.
If D is Female, the answer is Niece.
As the sex of D is not known, hence, the relation between D and A cannot be determined.
Note: Niece: A daughter of one's brother or sister, or of one's brother-in-law or sister-inlaw. Nephew: A son of one's brother or sister, or of one's brother-in-law or sister-in-law.